Instrumentation amplifier
Instrumentation amplifier with circuit equations and operating-limit checks.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Three-op-amp gain: G = (1 + 2R/Rg) Gdifference
Two-op-amp internal node: A = 1/(G−1); V1 = (1+A)V− − A Vref
Output: Vout = Vref + G(V+ − V−)
Assumptions
- Three-op-amp nodes are Vcm ± Gfront Vdiff/2. Two-op-amp mode is the cascade with first-stage gain 1+A and second-stage subtracting ratio 1/A. Integrated choices provide nominal gain constants only; their true internal headroom needs device-specific limits. The plotted region intersects the input and internal-output limits for the selected ideal architecture. REF pin error uses a user-specified pin current.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Architecture
- three
- Positive input
- 0.505 V
- Negative input
- 0.495 V
- Reference voltage
- 0 V
- Front-end feedback resistor
- 25000 Ω
- Gain resistor
- 1000 Ω
- Three-op-amp difference-stage gain
- 1
- Upper internal/output limit
- 13 V
- Lower internal/output limit
- -13 V
- Input common-mode upper limit
- 12 V
- Input common-mode lower limit
- -12 V
- Reference drive resistance
- 0 Ω
- Reference pin current
- 0 A
Results
- Output
- 0.51 V
- Differential gain
- 51
- First internal output
- 0.245 V
- Second internal output
- 0.755 V
- Reference source error
- 0 V